I would not waste my money on polyester junk. Merino wool is by far the best stuff I have ever used and everyone I have talked too that has tried merino wool will never go back to under armor or anything like it. Wear the merino wool next to your skin. People think you need to where some kind of polyester next to your skin then the wool but that is false. Merino wool wicks moisture like other products wishes they could and leaves you feeling dry and warm. First Lite and Minus 33 are good brands to look into. I have the Minus 33 expedition weight and it is very nice.

I'd agreed with chaded on merino being the best choice for a baselayer.

OMER Cold water dry suit
 

Just check out this "Omer Red Stone Jacket 7 mm", this has been designed to give you maximum protection in very cold waters since it offers a warm feeling, comfort, freedom of movement, and the camouflage design makes it ideal for spearfishing.